# Python imports
import json

# Django imports
from django.utils import timezone
from django.db.models import Q, OuterRef, F, Func, UUIDField, Value, CharField, Subquery
from django.core.serializers.json import DjangoJSONEncoder
from django.db.models.functions import Coalesce
from django.contrib.postgres.aggregates import ArrayAgg
from django.contrib.postgres.fields import ArrayField

# Third Party imports
from rest_framework.response import Response
from rest_framework import status

# Module imports
from .. import BaseViewSet
from plane.app.serializers import IssueRelationSerializer, RelatedIssueSerializer
from plane.app.permissions import ProjectEntityPermission
from plane.db.models import (
    Project,
    IssueRelation,
    Issue,
    FileAsset,
    IssueLink,
    CycleIssue,
)
from plane.bgtasks.issue_activities_task import issue_activity
from plane.utils.issue_relation_mapper import get_actual_relation


class IssueRelationViewSet(BaseViewSet):
    serializer_class = IssueRelationSerializer
    model = IssueRelation
    permission_classes = [ProjectEntityPermission]

    def list(self, request, slug, project_id, issue_id):
        issue_relations = (
            IssueRelation.objects.filter(
                Q(issue_id=issue_id) | Q(related_issue=issue_id)
            )
            .filter(workspace__slug=self.kwargs.get("slug"))
            .select_related("project")
            .select_related("workspace")
            .select_related("issue")
            .order_by("-created_at")
            .distinct()
        )
        # get all blocking issues
        blocking_issues = issue_relations.filter(
            relation_type="blocked_by", related_issue_id=issue_id
        ).values_list("issue_id", flat=True)

        # get all blocked by issues
        blocked_by_issues = issue_relations.filter(
            relation_type="blocked_by", issue_id=issue_id
        ).values_list("related_issue_id", flat=True)

        # get all duplicate issues
        duplicate_issues = issue_relations.filter(
            issue_id=issue_id, relation_type="duplicate"
        ).values_list("related_issue_id", flat=True)

        # get all relates to issues
        duplicate_issues_related = issue_relations.filter(
            related_issue_id=issue_id, relation_type="duplicate"
        ).values_list("issue_id", flat=True)

        # get all relates to issues
        relates_to_issues = issue_relations.filter(
            issue_id=issue_id, relation_type="relates_to"
        ).values_list("related_issue_id", flat=True)

        # get all relates to issues
        relates_to_issues_related = issue_relations.filter(
            related_issue_id=issue_id, relation_type="relates_to"
        ).values_list("issue_id", flat=True)

        # get all start after issues
        start_after_issues = issue_relations.filter(
            relation_type="start_before", related_issue_id=issue_id
        ).values_list("issue_id", flat=True)

        # get all start_before issues
        start_before_issues = issue_relations.filter(
            relation_type="start_before", issue_id=issue_id
        ).values_list("related_issue_id", flat=True)

        # get all finish after issues
        finish_after_issues = issue_relations.filter(
            relation_type="finish_before", related_issue_id=issue_id
        ).values_list("issue_id", flat=True)

        # get all finish before issues
        finish_before_issues = issue_relations.filter(
            relation_type="finish_before", issue_id=issue_id
        ).values_list("related_issue_id", flat=True)

        queryset = (
            Issue.issue_objects.filter(workspace__slug=slug)
            .select_related("workspace", "project", "state", "parent")
            .prefetch_related("assignees", "labels", "issue_module__module")
            .annotate(
                cycle_id=Subquery(
                    CycleIssue.objects.filter(
                        issue=OuterRef("id"), deleted_at__isnull=True
                    ).values("cycle_id")[:1]
                )
            )
            .annotate(
                link_count=IssueLink.objects.filter(issue=OuterRef("id"))
                .order_by()
                .annotate(count=Func(F("id"), function="Count"))
                .values("count")
            )
            .annotate(
                attachment_count=FileAsset.objects.filter(
                    issue_id=OuterRef("id"),
                    entity_type=FileAsset.EntityTypeContext.ISSUE_ATTACHMENT,
                )
                .order_by()
                .annotate(count=Func(F("id"), function="Count"))
                .values("count")
            )
            .annotate(
                sub_issues_count=Issue.issue_objects.filter(parent=OuterRef("id"))
                .order_by()
                .annotate(count=Func(F("id"), function="Count"))
                .values("count")
            )
            .annotate(
                label_ids=Coalesce(
                    ArrayAgg(
                        "labels__id",
                        distinct=True,
                        filter=Q(
                            ~Q(labels__id__isnull=True)
                            & (Q(label_issue__deleted_at__isnull=True))
                        ),
                    ),
                    Value([], output_field=ArrayField(UUIDField())),
                ),
                assignee_ids=Coalesce(
                    ArrayAgg(
                        "assignees__id",
                        distinct=True,
                        filter=Q(
                            ~Q(assignees__id__isnull=True)
                            & Q(assignees__member_project__is_active=True)
                            & Q(issue_assignee__deleted_at__isnull=True)
                        ),
                    ),
                    Value([], output_field=ArrayField(UUIDField())),
                ),
            )
        ).distinct()

        # Fields
        fields = [
            "id",
            "name",
            "state_id",
            "sort_order",
            "priority",
            "sequence_id",
            "project_id",
            "label_ids",
            "assignee_ids",
            "created_at",
            "updated_at",
            "created_by",
            "updated_by",
            "relation_type",
        ]

        response_data = {
            "blocking": queryset.filter(pk__in=blocking_issues)
            .annotate(relation_type=Value("blocking", output_field=CharField()))
            .values(*fields),
            "blocked_by": queryset.filter(pk__in=blocked_by_issues)
            .annotate(relation_type=Value("blocked_by", output_field=CharField()))
            .values(*fields),
            "duplicate": queryset.filter(pk__in=duplicate_issues)
            .annotate(relation_type=Value("duplicate", output_field=CharField()))
            .values(*fields)
            | queryset.filter(pk__in=duplicate_issues_related)
            .annotate(relation_type=Value("duplicate", output_field=CharField()))
            .values(*fields),
            "relates_to": queryset.filter(pk__in=relates_to_issues)
            .annotate(relation_type=Value("relates_to", output_field=CharField()))
            .values(*fields)
            | queryset.filter(pk__in=relates_to_issues_related)
            .annotate(relation_type=Value("relates_to", output_field=CharField()))
            .values(*fields),
            "start_after": queryset.filter(pk__in=start_after_issues)
            .annotate(relation_type=Value("start_after", output_field=CharField()))
            .values(*fields),
            "start_before": queryset.filter(pk__in=start_before_issues)
            .annotate(relation_type=Value("start_before", output_field=CharField()))
            .values(*fields),
            "finish_after": queryset.filter(pk__in=finish_after_issues)
            .annotate(relation_type=Value("finish_after", output_field=CharField()))
            .values(*fields),
            "finish_before": queryset.filter(pk__in=finish_before_issues)
            .annotate(relation_type=Value("finish_before", output_field=CharField()))
            .values(*fields),
        }

        return Response(response_data, status=status.HTTP_200_OK)

    def create(self, request, slug, project_id, issue_id):
        relation_type = request.data.get("relation_type", None)
        if relation_type is None:
            return Response(
                {"message": "Issue relation type is required"},
                status=status.HTTP_400_BAD_REQUEST,
            )

        issues = request.data.get("issues", [])
        project = Project.objects.get(pk=project_id)

        issue_relation = IssueRelation.objects.bulk_create(
            [
                IssueRelation(
                    issue_id=(
                        issue
                        if relation_type in ["blocking", "start_after", "finish_after"]
                        else issue_id
                    ),
                    related_issue_id=(
                        issue_id
                        if relation_type in ["blocking", "start_after", "finish_after"]
                        else issue
                    ),
                    relation_type=(get_actual_relation(relation_type)),
                    project_id=project_id,
                    workspace_id=project.workspace_id,
                    created_by=request.user,
                    updated_by=request.user,
                )
                for issue in issues
            ],
            batch_size=10,
            ignore_conflicts=True,
        )

        issue_activity.delay(
            type="issue_relation.activity.created",
            requested_data=json.dumps(request.data, cls=DjangoJSONEncoder),
            actor_id=str(request.user.id),
            issue_id=str(issue_id),
            project_id=str(project_id),
            current_instance=None,
            epoch=int(timezone.now().timestamp()),
            notification=True,
            origin=request.META.get("HTTP_ORIGIN"),
        )

        if relation_type in ["blocking", "start_after", "finish_after"]:
            return Response(
                RelatedIssueSerializer(issue_relation, many=True).data,
                status=status.HTTP_201_CREATED,
            )
        else:
            return Response(
                IssueRelationSerializer(issue_relation, many=True).data,
                status=status.HTTP_201_CREATED,
            )

    def remove_relation(self, request, slug, project_id, issue_id):
        related_issue = request.data.get("related_issue", None)

        issue_relations = IssueRelation.objects.filter(
            workspace__slug=slug,
        ).filter(
            Q(issue_id=related_issue, related_issue_id=issue_id)
            | Q(issue_id=issue_id, related_issue_id=related_issue)
        )
        issue_relations = issue_relations.first()
        current_instance = json.dumps(
            IssueRelationSerializer(issue_relations).data, cls=DjangoJSONEncoder
        )
        issue_relations.delete()
        issue_activity.delay(
            type="issue_relation.activity.deleted",
            requested_data=json.dumps(request.data, cls=DjangoJSONEncoder),
            actor_id=str(request.user.id),
            issue_id=str(issue_id),
            project_id=str(project_id),
            current_instance=current_instance,
            epoch=int(timezone.now().timestamp()),
            notification=True,
            origin=request.META.get("HTTP_ORIGIN"),
        )
        return Response(status=status.HTTP_204_NO_CONTENT)
